Electrical control system



June 17, 1952 w plcKlNG 2,601,002

.ELECTRICAL CONTROL SYSTEM Filed July 24, 194e 2 SHEETS- SHEET 1 MA/N AC .ee BY pwa June 17, 1952 J. w. PlcKlNG 2,601,002

ELECTRICAL CONTROL SYSTEM 39 IODIO lol i7' J o; vanaaf 23 C@- Y INVENTOR.

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Patented June 17, 1952 ELECTRICAL CONTROL SYSTEM .ay W. icking, Cleveland, Ohio,l assi :nor to The Reliance Electric & Engineering corporation i Ohio ompany, a

Application July 24, 1946, Serial o. 685,948

(Cl. g1g-154) A 20 Claims. l

invention relates in general to electrical control systems and more particularly to electrieal control systems adapted to control the speed of an electric motor or the voltage output of o. generator.

An object of my invention is the provision of an electrical control circuit for substantially linearly varying the speed of an electric motor or for linearly varying the operation of a dynamoelectric machine.

Another object of my invention is to give substantially linearly variable speed control to a direct current motor to any predetermined speed from a relatively low value to a relatively high value compared to the rated speed of the motor.

Another object of my invention is the provision of an electrical control system to give substantially linearly variable speed control at a predeterminable variable rate to an electric motor to any predeterminable speed. n

Another object of my invention is the provision of an electrical control system yfor substantially constant acceleration or deceleration of a direct current motor at a predeterminably variable rate to any piedeterrninable speed, the direct current electrical energy for the motor coming from a direct current generator, the fields of the direct current motor and generator lbeing separately excited and controlled by the said elec-v trical control system.

Another object of my invention is an electrical control circuit to linearly vary the speed of a direct current electric motor which derives its power from a motor generator set, wherein the speed control is obtained by linearly varying the output voltage of the direct current generator for below rated speeds ofy the electric motor, and an automatic change-over is accomplished in the control circuit to control the excitation of the motor field for speeds above the rated speed of the said electric motor.

Other objects and a fuller understanding of my invention may be had by referring to the follow'- ing description and claims, taken in conjunction with the accompanying drawing, in which:

Figure 1 diagrammatically represents an electrical control system embodying my invention;

Figure 2 diagrammatically represents a simplined embodiment of my invention; and

Figure 3 diagrammatically' represents another simplied circuit using my invention.

With reference to Figurel a motor Il drives a load l2, the motor Il deriving its power from; a generator i3. The generator i3 is driven from a prime mover I4. The generator I3 has a field I5, the field l5 deriving its power from a first excitation means I6. The motor Il has a field Il, the field l1 deriving its power from a second excitation means i8. A main alternating current source of voltage 22 supplies energy for both the erst and second excitation 'means ls and I8. The iirst excitation means I6 for exciting the generator field l5 includes a first and second gaseous discharge device With 'reference Characters 23 and 24 respectively, and the second excitation means i8 for the motor field Il includes a third and fourth gaseous discharge device with reference characters 25 and 26 respectively. With two gaseous discharge devices for each excitation means, full Wave rectification is thereby obtained. The first gaseous discharge device 23 has a cathode 21, a control grid 28 and an anode 29. The second gaseous discharge device 24 has a cathode 30, a control grid 3| and an anode 32. The third gaseous discharge device 25 has a cathode 33, a control grid 34 and an anode 35. The fourth gaseous discharge device 25 has a cathode 36, a control grid 31 and an anode 38. A main transformer 39 for supplying electrical energy to the first and second excitation means has' a primary Winding 40, a first secondary winding 4I and a second secondary Winding 42|. IIfhe primary winding 40 of the main transformer 39 is connected through a switch 43 to the main A. C. source of voltage 22. The first secondary winding 4| of the main transformer 39 has end terminals 44 and 45, a midtap 46, and two sup'- plem'entary taps 41 and 48, one on either side of the midtap 46. The second secondary Winde ing 42 'of the main transformer 33 has end terminals 49 and 50, a midtap 5|, and supplementary taps 52 and 53, one on either side of the midtap 5l. To complete the full wave rectifier circuit of the first excitation means. the cathodes 21 and 30 of the first and second gaseous discharge devices are connected together to one end of the generator field i5 at the connection 68. The other end of the generator iield i5 being con-V nected to the lrnidtap 46 of the first secondary winding 4l of the main transformer 39, and the anodes 29 and 32 of the first and second gaseous discharge devices are connected to the end terminals 44 and 45 of the first secondary winding 4I of the main transformer 39. To complete the full wave rectifier circuit of the second ex# citation means, the cathodes 33 and 36 of the third and fourth gaseous discharge devices 25 and 26 are connected together to one end of the motor field Il, at the connection G9, the other end of the motor eid il being connected to the midtap 5| of the second secondary Winding 42 of the main transformer 39, and the anodes and 38 of the third and fourth gaseous discharge devices 25 and 25 are connected to the end terminals 49 and 59 of the second secondary winding 42 of the main transformer 39. In the first excitation means I6, a first transformer 54 has a primary winding 12 and a secondary winding 13. The secondary winding 12 is connected to the supplementary taps 41 and 48 of the first secondary winding 4I of the main transformer 39. In the second excitation means I8, a second transformer 55 has a primary winding 14 and a secondary winding 15. The primary winding 14 is connected to the supplementary taps 52 g and 53 of the second secondary Winding 42 of the main transformer 39. A control means |9 includes a first and second grid circuit means 20 and 2| whereby the first grid circuit means 28 impresses a first A. C. potential between the cathodes and control grids of the first and second gaseous devices, and the second grid circuit means '2| impresses a second A. C. potential between the cathodes and control grids of the third and fourth gaseous discharge devices. The first grid circuit means 28 comprises the secondary winding 13 of the first transformer 54, first and second control grid resistors 58 and 59, and a condenser 55. The iirst and second control grid resistors 58 and 59 are connected in series between the control grids 28 and 3| of the first and secondi gaseous discharge devices 23 and 24. The control grid 28 connects to the first control grid resistor 58 at the connection 82, the first and second control grid resistors connect together at the connection 63, and the second control grid resistor 59 is connected toi the control grid 3| at the connection 84. |The condenser 56 is connected between the connection 62 and one end of the secondary winding 'i3 of the first transformer 54, and the other end of the secondary winding 13 is connected to the connection 84. The second grid circuit means 2| comprises the secondary winding 15 of the second transformer 55, a third and fourth control grid resistor and 6|, and a condenser 51. The third and fourth control grid resistors 69 and 6| are connected in series between the control grids 34 and 31 of the third and fourth gaseous discharge devices 25 and 26. to the third control grid resistor 68 at the connection 65, the third and fourth control grid resistors 60 and 6| connect together at connection 65 and the fourth control grid resistor 6| connects to the control grid 31 at the connection 61. The condenser 5'! is connected between the connection 65 and one end of the secondary winding 15 of the second transformer 55, and the other end of the secondary winding 15 is connected to the connection 61. Upon energization of the first and second transformers 54 and 55, a first alternating current potential is developed in the first grid circuit means 20 across the first control grid resistor 58 and across the second control grid resistor 59, and a second alternating current potential is developed in the second grid circuit means 2| across the third control grid resistor 68 and across the fourth control grid resistor 6|. The first alternating current potential is impressed between the cathodes and control grids of the first and second gaseous discharge devices 23 and 24, and the second A. C. potential is impressed between the cathodes and the control grids of the third and fourth gaseous discharge devices 25 and 26. By so impressing The control grid 34 connects an A. C. potential between the said cathodes and said control grids, a basis is established for controlling the rectified output of the gaseous discharge devices, thereby controlling the amount of excitation of the first and second excitation means, and thereby varying the speed of the motor A potential source 16 is used to modify the control means |9. A voltage dividing circuit 11 is connected between the potential source 16 and the control means I9. An impedance matching circuit 18 is used to couple the potential source 16 to the voltage dividing circuit 11. The potential source 18 is a circuit that generates an essentially linearly variable voltage across a condenser 19. The voltage across the condenser 19 is applied through the impedance matching circuit 18 to the voltage dividing circuit 11, which divides this voltage into a first and second output voltage for modifying the iirst and second A. C. potentials impressed between the cathodes and control grids of the gaseous discharge devices of the first `and second excitation means respectively.

The potential source 16 is substantially the same as my Linear Voltage Generator, Serial No. 685,947. now Patent No. 2,505,688, dated April 25, 1950, filed on even date herewith.

The potential source 16 comprises a bridge rectifier 8|, a thermionic pentode tube 82 across the output terminals of the bridge rectifier 8|, the condenser 19 and a unidirectional high voltage source 89, the condenser 19 and the unidirectional high voltage source 80 being disposed in series circuit relationship across the input terminals of the bridge rectifier 8|. The bridge rectifier 8| has a first input terminal 85 and a second input terminal 86, a first output terminal 83 and a second output terminal 84. The bridge rectifier 8| has first, second, third, and fourth unidirectional current passing devices with reference numbers 81, 88, 89 and 90 respectively. In the description, current will be assumed to iiow in the same direction as the electrons, and current and electron current will be synonymous. The first unidirectional current passing device 81 is connected to pass electron current from the first output terminal 83 to the first input terminal 85. The second inidirectional current passing device 88 is connected tol pass electron current from the first output terminal 83 to the second input terminal 86. The third unidirectional current passing device 89 is connected to pass electron current from the first input terminal to the second output terminal 84; and the fourth unidirectional current passing device 90 is connected to pass electron current from the second input terminal 8B to the second output terminal 84. Th-e thermionic pentode tube 82 has a cathode 9|, an anode 92, a control grid 93, a screen grid 94, and a suppressor grid 95. The anode 92 of the thermionic pentode tube 82 is connected to the first output terminal 83, and the cathode 9| is connected to the second output terminal 84 of the bridge rectifier 8|. A D. C. supply source 96 supplies D. C. potential to the screen grid 94 and the,I control grid 93 of the thermionic pentode tube 82. The D. C. supply source 96 has a positive terminal 91 and a negative terminal 98. Connected across these terminals of the D. C. supply source 96 is a screen grid potential resistor 99, a control grid potential limiting resistor |00 and a control grid potentiometer |0| in series. A connection |02 connects the positive end of the screen grid potential resistor 99 to the positive terminal 91 of the D. C'. supply source 96. A connection 03 connects the negative end of the screen grid potential resistor 99 to the positive end of the control grid potential limiting resistor |00. A connection |04 connects the positive end of the control grid potentiometer |I to the negative end of the control grid potential limiting resistor |00. The negative end of the control grid potentiometer |0| is connected to the negative terminal 98 of the D. C. supply source 96. The screen grid potential which appears at the positive terminal 91 of the D. C. supply source 96 and at the connection |02, is applied to the screen 94 of the thermionic pentode tube 82 through the current limiting resistor |05. The cathode 9| of the thermionic pentode tube 82 is connected through the conductor |06 to the connection |03 between the resistor 99 and |00, to provide the reference voltage for the cathode 9|. The control grid 93 is connected through the conductor |01 to the movable finger |08 on the potentiometer |0I, to provide a variable negative voltage on the control grid 93 with respect to the cathode 9| of the thermionic pentode tube 821. The control grid potential limiting resistor |00 prevents the negative potential of the control grid 93 with respect to the cathode 9| from becoming too small a value. The suppressor grid 95 is connected through a conductor |09 to the cathode 9|. The condenser 19 has a first terminal A and a second terminal B. The second terminal B is connected to the first input terminal 85 of the bridge rectiiier 8|. The unidirectional high voltage source 80 has a negative terminal I |0 and a positive terminal III. The iirst terminal A of the condenser 19 is connected to the negative terminal IIO of the unidirectional high voltage source 80 through a conductor ||2. A voltage dividing resistor I |3 is connected across the terminals IIO and III of the unidirectional high voltage source 80. The voltage dividing resistor I3 has two end terminals I4 and |5, and three intermediate terminals I|6, ||1 and ||8. The end terminal ||4 of the voltage dividing resistor ||3 is connected to the negative terminal ||0 of the unidirectional high voltage source 80, and the other end terminal I|5 is connected to the positive terminal I| A potentiometer ||9 is connected between the terminals ||4 and ||8 of the voltage dividing resistor |I3. A single pole double throw switch |20 is connected to either include or exclude the unidirectional high voltage source 80 from the series circuit arrangement, and has a first connection |2|, a second connection |22, a common connection |23 and a contact member |24. A movable nger |25 of the potentiometer IIS is connected to the second connection |22 of the switch |20. A conductor |26 connects the rst terminal |2I of the switch |20 to the end terminal I|4 of the voltage dividing resistor ||3. A conductor |21 connects the common connection |23 of the switch |20 and the second input terminal 86 of the bridge rectier 8|.

As hereinbefore stated the potential developed across the terminals A and B of the condenser 19 is applied through an impedance matching circuit 18 to the voltage dividing circuit 11. The

triode tube |28, and the voltage output which is "j supplied to the voltage dividing circuit 11 is developed across a cathode resistor |32, which is in series circuit relationship with the condenser 19 and the triode tube |28. The cathode resistor |32 has an upper terminal |33 and a lower terminal |34. The upper terminal |33 of the cathode resistor |32 is connected to the cathode |29 of the thermionic triode tube |28. The lower terminal |34 of the cathode resistor |32 is connected through conductor |35 to the mid-terminal I6 of the voltage dividing resistor I 3. The control grid |30 of the thermionic triode tube |28 is connected through conductor |36 to the terminal B of the condenser 19. The anode |3| of the thermionic triode tube |28 is connected through conductor |31 to the end or positive terminal I I5 of the voltage dividing resistor I |3.

The impedance matching circuit 18 matches the high impedance of the potential source 19 to the lower impedance of the voltage dividing circuit 11. The voltage dividing circuit 11 is substantially the same as my Volta-ge Dividing Circuit, Serial No- 685,945, now abandoned, iiled on even date herewith. The voltage of the impedance matching circuit 18 which is applied to the voltage dividing circuit 11 is obtained across the cathode resistor |32. The voltage dividing circuit 11 comprises a biasing potential source |38, a thermionic diode tube |39 and a resistor |40 in series circuit arrangement. The biasing potential source |38 has a positive terminal |4| and a negative terminal |42. The thermionic diode tube |39 has a cathode |43 and an anode |44. The resistor |40 has an upper terminal |45 and a lower terminal |46. The positive terminal |4| of the biasing potential source |38 is connected through a conductor |41 to the upper terminal |33 of the cathode resistor |32. The negative terminal |42 of the biasing potential source |38 is connected through conductor |49 to the anode |44 of the thermionic diode tube |39. The cathode |43 of the thermionic diode tube |39 is connected to the upper terminal |45 of the resistor |40. A conductor |48 connects the lower terminal |46 of the resistor |40 to the lower terminal |34 of the cathode resistor |32.

As hereinbefore stated, the voltage dividing circuit 11 has a iirst output voltage means and a second output voltage means, for modifying the irst and second grid circuit means A20 and 2| of the control means I9 and thereby modifying the output of the rst and second excitation means respectively. The first output voltage of the voltage dividing circuit 11 appears across the terminals |33 and |45, which terminals shall be termed the first and second output terminals respectively of the voltage dividing circuit 11, which voltage is across the combination of the biasing potential source |38 and the thermionic diode tube |39. The second output voltage of the voltage dividing circuit 11 appears across the terminals |45 and |46, which are the upper and lower terminals respectively of the resistor |40, which terminals shall be' termed the second and third output terminals, respectively, of the voltage dividing circuit 11.

A first regulatory means |50 is used to further modify the iirst grid circuit means 20 of the control means I9 and a second regulatory means |5| is used to further modify the second grid circuit means 2| of the control means I9. The first regulatory means |50 includes two resistors |52 and |53 in series across the output of the generator I3, so that a regulatory potential obtained across one of these resistors proportional to the voltage output of the generator I3 can be used to modify the voltage output of the generator I3 by modifying the first grid circuit means 20. The second regulatory means |5| includes two resistors |54 and |55 in series across the motor iield so that a regulatory potential obtained across one of these resistors, which will be proportional to the voltage applied to the motor iield I'I, can be used to modify the potential applied to the field Il, by modifying the second grid circuit means 2|.

The generator I3 has a negative terminal |56 and a positive terminal |51. The motor II has a negative terminal |58 and a positive terminal |59. The negative terminals |56 and |58 of the generator' and the motor I I respectively, are connected by a conductor |50. The positive terminals |51 and |50 of the generator I3 and the motor II, respectively, are connected by a conductor IBI. In the iirst regulatory means |50, a connection |02 joins one end each of the resistors |52 and |53. The other end of the resistor |52 is connected to the conductor at the connection |63, and the other end of the resistor |53 is connected to the conductor IBI at the connection |54. The second regulatory means |5| includes the resistors |54 and |55. The resistors |54 and |55 have one end each connected together at the connection |66. The other end of the resistor |54 is connected to the connection 'l0 of the motor field il, and the other end of the resistor |55 is connected to the connection 'II of the motor field I'I. The connection |66 which connects the two resistors |54 and |55 of the second regulatory means |5| is connected by the conductor |61 to the connection |62 which similarly connects the resistors |52 and |53 of the first regulatory means |50. A conductor |65 connects the connection |52 to the upper terminal |45 of the resistor |40, which is the second output terminal of the voltage dividing circuit 1T. To complete the circuit for impressing the modifying potentials of the iirst and second outputs of the voltage dividing circuit Il, and the regulatory potentials of the rst and second regulatory means upon the control means I9, the following connections and conductors are added: A conductor |68 is connected between the terminal ||'I of the voltage dividing resistor ||3 and the connection 66 between the third and fourth control grid resistors 60 and 6|; a conductor |69 is connected between the first output terminal of the voltage dividing circuit Il, which is the upper terminal |33 of the cathode resistor |32, and the connection 63 which connects the rst and second control grid resistors 58 and 59.

In actual operation, variations in the speed of the motor are accomplished by varying the setting of the movable finger |25 of the potentiometer ||9 in the potential source 16, and variations in the rate of acceleration or deceleration of the motor I are accomplished by varying the setting of the movable ringer |03 of the potentiometer |0| of the potential source 16. The circuit operation will start with the closing of the main switch 43, which causes electrical energy to flow from the -main AC source of voltage to the main transformer 39. This energization of the main transformer causes a potential to be impressed between the cathodes and anodes of the four gaseous discharge devices, which gaseous discharge devices will cause excitation current to flow in the respective fields of the generator and motor if the proper potential is impressed between the cathodes and control grids of the four gaseous discharge devices from the respective grid circuit means. In the first excitation means, as hereinbefore stated, the control voltage impressed between the cathodes and control grids of the iirst and second gaseous discharge devices is the first alternating current voltage, modified by the potential of the first output voltage means of the voltage dividing circuit Il, and the regulatory potential of the first regulatory means. In the second excitation means, the potential applied between the cathodes and control grids of the third and fourth gaseous discharge devices is a voltage from the voltage dividing resistor I I3 and the second alternating current potential, modied by the potential of the second output voltage means of the voltage dividing circuit 11 and the regulatory potential of the second regulatory means. The operation begins with closing the main switch 43, thereby energizing the main transformer 39 and the associated rectifier circuits of the first and second excitation means. with the assumption that the prime mover I4 is turning the generator' at rated speed. The switch |20 is then moved into the position so that the Contact member |24 contacts the second connection |22 to the common connection |23. This connection of the switch |20 permits the unidirectional high voltage source to charge the condenser' I9 to a predetermined voltage at a predetermined rate. The predetermined voltage is regulated by the setting of the movable ringer |25 of the potentiometer ||9, and the predetermined rate of charge is regulated by the setting of the movable linger' |08 of the potentiometer IOI. The actual operation of this potential source circuit I6 is as follows: Electron current flows from the negative terminal I|0 of the unidirectional high voltage source 80 through the conductor II2 to the terminal A of the condenser 19, through the condenser' 79, thereby charging this condenser 19, to the terminal B of the condenser I9 and then to the first input terminal of the bridge rectifier 8|, then through the third unidirectional current passing device 89 to the second output terminal `|44 of the bridge rectifier 3|, then from the cathode 9| to the anode 92 of the thermionc pentode tube B2 on to the first output terminal 83 of the bridge rectifier 8|, then through the second unidirectional current passing device 88 to the second input terminal 86 of the bridge rectifier 8 I, through the conductor |2'I, through the switch |20, the movable finger |25, through the right hand portion of the potentiometer |9 to the terminal ||8 of the voltage dividing resistor ||3, through the right hand portion of the voltage dividing resistor ||3 to the end terminal II5 of the voltage dividing resistor I|3, then return to the positive terminal of the unidirectional high voltage source y8|). The constant current passing characteristic of a thermionic pentode tube is utilized in this circuit in order to charge the condenser at an essentially uniform rate. It will be seen that as the condenser 'I9 char'ges through the passage of the aforementioned electron current, the resultant voltage applied across the cathode 9| and anode 92 of the thermionic pentode tube 82 will decrease. This decrease in applied potential across the thermionic pentode tube 82 does not materially aiect the rate of passage of current, due to the essentially constant current passing characteristic of the thermionic pentode tube. The condenser I9 will charge to a potential equal to the potential setting of the movable ringer |25 of the potentiometer I|9 at an essentially linear' rate. This charging rate will remain essentially constant for any given setting conditions. This charging rate may be varied however by the setting of the movable linger I 08 of the potentiometer which varies the effective negative potential applied to the control grid 93 with respect to the cathode 9| of the thermionic pentode tube 82. Variations in the setting of this movable finger |08 of the potentiometer |0| cause a more or less negative potential to be applied to the control grid 93 with respect to the cathode 9| and thereby a smaller or larger current respectively is allowed to pass through the tube 82. This variable potential across the terminals A and B of the condenser 19 is applied through the impedance matching circuit 18 to the voltage dividing circuit 11. This potential across the terminals A and B of the condenser 19 will be of the polarity such that the terminal A will be negative and the terminal B will be positive. This potential across the condenser 19 is applied between the control grid and the cathode of the thermionic triode tube |28 'of the impedance matching circuit 18. The potential applied between the control grid |30 and the cathode |29 of the thermionic triode tube |28 controls the amount of current passed by this thermionic triode tube |28. The potential impressed between the anode |3| and the cathode |29 is a constant value, being supplied from the unidirectional high voltage source 80. The potential of the condenser 19 is applied between the control grid and cathode of the thermionic triode tube |28 through a portion of the voltage dividing resistor |3 which is of opposite polarity to the potential ci the condenser 19. This portion of the voltage dividing resistor ||3 is that portion between the terminal ||6 and the end terminal I|4, which applies a negative potential to the grid |30 with respect to the cathode |29. This biases the control grid negatively, and prevents current ilow through the tube |28 until the potential across the condenser 19 becomes of suiiicient value to adequately oppose the potential developed across that section of the voltage dividing resistor H3 between the terminals H4 and IIS. The potential impressed between the control grid |30 and the cathode |29 by the portion of the voltage dividing resistor ||3 between the terminals ||4 and ||'6 alone, is sufficiently negative to prevent any current ilow between the cathode and anode |3| of the thermionic triode tube |28. As the potential across the condenser 19 increases, a point is reached where the negative potential applied to the control grid|30 with'respect to the cathode |29 is sufliciently small to permit passage of current between the .cathode |29 and the anode |3I. As the potential across the condenser 19 continues to increase, the control gird |30 becomes increasingly less negative with respect to the cathode |29, thereby permitting continually increasing amounts of current to pass between the cathode |29 and the anode |35. This passage of current from the cathode |29 to the anode |3| of the thermionic triode tube |29 will start at the negative terminal H3 of the unidirectional high voltage source 03, through the conductor ||2 to the end terminal i of the voltage dividing resistor I3, through a part of the voltage dividing resistor ||3 to the terminal i6 thereof, then through the conductor 35, through the cathode resistor |32, through the tube |28 from the cathode |29 to the anode 13|, through the conductor |31 and return to the positive terminal of the unidirectional high '.551

thermionic diode tube |39.

voltage source 80. This flow of current causes a voltage drop across the cathode resistor |32. This voltage drop is therefore the voltage that is applied to the voltage dividing circuit 11. This voltage drop will increase or decrease in direct proportion to the potential change across the condenser 19. The action of the voltage dividing circuit 11 is such that the potential developed across the cathode resistor |32 is impressed upon the series circuit of the voltage dividing circuit 11 consisting of the biasing potential source |38, the thermionic diode tube |39, and the resistor |40. The passage of the electron current through the impedance matching circuit 18 has caused the lower terminal |34 of the cathode resistor to be negative with respect to the upper terminal |33, This voltage therefore is connected in the series circuit arrangement of the voltage dividing circuit 'il in such a manner that the positive potential is impressed upon the anode |44 of the thermionic diode tube |39, and the negative potential is impressedupon the cathode |43 of this However, the biasing potential source |33 is so connected in the series circuit arrangement that a negative potential is applied to the anode |44 of the thermionic diode tube i3d. Therefore this negative potential from the biasing potential source |38 being applied to the ano'de |44 of the thermionic diode tube |39 prevents the anode |44 from being positive with respect to the cathode |43 until the potential across the cathode resistor |32 exceeds the potential of the biasing potential source. Until the potential across the cathode resistor |32 exceeds the biasing potential source |38, no current is passed by the thermionic diode tube |39. Under these conditions, the impedance of the thermionic diode tube 39 is very high. When the potential across the cathode resistor |32 exceeds the poten tial ci the biasing potential source, and the thermionic diode tube passes current, a voltage drop will occur across the resistor |40. This voltage drop across the resistor |40, caused by the passage of current, is the second output voltage means, The rst output voltage appears across the nrst and second output terminals which are terminals |33 and |45, and for all values of the 'voltage across the cathode resistor |32 below the potential of the biasing potential source |38 the first output voltage will be substantially equal to this voltage, because the thermionic diode tube |39 will not pass current and therefore there will be no voltage drop across the resistor |40. For values of the voltage applied across the cathode resistor |32 greater than the potential of the biasing potential source, the thermionic diode tube |39 conducts current, thereby having a low impedance, and the rst output voltage will substantially equal the potential of the biasing potential source |38. The first output voltage will therefore remain constant at the potential oi the biasing potential source for all values of the voltage drop across the cathode resistor |32 in excess of the potential of the biasing potential source ist. The second output voltage which is across the resistor |153, will be zero in value for all. values of the potential across the cathode resistor |32 below the potential of the biasingt potential source |38, because the thermionic diode tube |39 will not pass any current to perinit a voltage drop across the resistor |40. When the potential across the cathode resistor |32Vexceeds the potential of the biasing potential source Sii the thermionic diode tube thereby passing current, there will be a voltage drop caused by this passage of current across the resistor |40, and therefore there will be a second output voltage. This second output voltage will therefore be substantially equal to the incoming voltage across the cathode resistor |32 minus the potential of the biasing potential source |38. From the foregoing description is can be seen that the operation of the 'voltage dividing circuit 'I'I is such that an incoming signal voltage is divided into a first and second output voltage at a definite transition value governed by the potential of the biasing potential source |38. The first output voltage will vary directly with the incomingr signal voltage for all values of the incoming signal voltage less than the transition value, and remain at that transition value for all values of the incoming signal voltage greater than the transition value. The second output voltage will remain at zero for all values of the incoming signal voltage below the transition value, which first and second excitation means I6 and I8, and r therefore vary the speed of the motor A first alternating current potential is developed across the terminals 63 and 62, and the terminals 63 and 64 of the first and second control grid resistors 58 and 59, from the potential of the secondary winding 'I3 of the first transformer 54 and the first phase shifting condenser 56, which elements comprise the first grid circuit means 20. This first alternating current potential will be out of phase with the main alternating current source of voltage, because of the action of the first phase shifting condenser 56. This will have the effect of shifting the phase of the potential applied between the control grids and cathodes of the first and second gaseous discharge devices with respect to the alternating current voltage impressed between the cathodes and anodes of these same gaseous discharge devices. The potential of the first regulatory means will be the potential developed across the resistor |53 by the output voltage of the generator I3, and assuming the potential of the voltage output of the generator I3 to be as shown in Figure l, the connection |62 will be negative with respect to the connection |64,

which connections are across the resistor |53. The regulatory potential developed across this resistor |53 is so connected in the circuit to impress a negative voltage upon the control grid with respect to the cathode of the first and second gaseous discharge devices 23 and 24. This will have the effect of lowering the reference voltage of the first alternating current potential with respect to the main alternating current source of voltage. The potential of the first output voltage means from the voltage dividing circuit I'I is so connected in the circuit arrangement so that a positive potential is impressed upon the control grid with respect to the cathode. The first output voltage will therefore have the effect of tending to raise the reference voltage of the first alternating current potential with respect to the reference potential of the main alternating current source of voltage. To trace the circuit connections of the first grid circuit means, starting with the cathode 21 and 30 of the first and second gaseous discharge devices 23 and 24, the circuit extends through the connection 68 at one end of the generator field line I8, then to the positive terminal |5I of the generator I3, the connection |64, through the resistor |53 wherein a negative potential of the first regulatory means is impressed, to the connection |62, through the conductor |65 to the upper terminal |45 of the resistor |40, through the resistor |40, wherein a negative voltage, ir" any, is applied, to the lower terminal |46 of this resistor |40, through the conductor |48 to the lower terminal |34 of the cathode resistor |32, through the cathode resistor |32 where a positive potential is impressed from the first output voltage, to the upper terminal |33 of the cathode resistor |32, through the conductor |69 to the connection |63 and thence return to the respective control grids 28 and 3| through the first and second control grid resistors 58 and 59, wherein an alternating current potential of the first alternating current source is impressed. The result of the combination of these three voltages applied between the cathodes and control grids of the first and second gaseous discharge devices 23 and 24 of the first excitation means is follows:

The linearly variable voltage generated by the potential source 16 across the condenser I9 is applied through the first output voltage means of the voltage dividing circuit I'I also as a substantially linearly variable voltage, and has a tendency to raise the reference potential of the control grid-cathode voltage with respect to the anode-cathode voltage, which will have a tendency to make the gaseous discharge devices fire earlier in the cycle, because the critical grid potential of the gaseous discharge devices is exceeded increasingly earlier in the cycle of the alternating current voltage between the anodes and cathodes; this tendency to fire or trigger the gaseous discharge devices earlier in the cycle will tend to increase the excitation of the first excitation means, which means an increase in the excitation of the generator field I5, and a consequent tendency to increase the voltage output of the generator I3. As the generator voltage tends to rise, the potential of the first regulatory means will also tend to rise, which potential tends to lower the reference potential of the grid-cathode voltage with respect to the anodecathode voltage, therefore tending to make the gaseous discharge devices fire or trigger later in the cycle, thereby reducing the excitation supplied to the -generator field I5, and consequently the generator output voltage. Of these two opposing tendencies, the first output voltage of the voltage dividing circuit is the stronger, because of the increasing voltage output of the first output voltage. The result is an essentially linear increase in the generator output voltage at a rate established by the setting of the movable finger |08 of the potentiometer IOI of the potential source 16, and to a voltage output regulated by the setting of the movable nger |25 of the potentiometer |I9 of the potential source '|6. The potential of the biasing potential source |38 of the voltage dividing circuit 'I'I will be made such that the transition value regulated by this potential, and at which value the second output voltage begins to appear, will be just sufficient to permit rated output voltage of the generator I3 and consequent rated speed of the motor |I. This transition value between the first 13 N and second output voltages of the voltage dividing circuit 11 has the effect of an automatic change over from control of the rst excitation means to the control of the second excitation means, in order to obtain higher than rated speeds of the motor |I by modifying the second grid circuit means 2| of the control means I9 of the second excitation means I8 for the motor iield As hereinbefore stated, the second grid circuit means 2| includes the secondary winding 'l5 of the second transformer 55, the second phase shifting condenser 5l, the third and fourth control grid resistors 63 and 6|, and a portion of the voltage dividing resistor I3, modified by the second regulatory means |5| and the second output voltage means of the voltage dividing circuit This second grid circuit means 2| operates in substantially the same manner as the first grid circuit means 25. A second alternating current potential is developed across the resistors 6! and 6|, from the secondary winding 'l5 of the second transformer 55 and the second phase shifting condenser 51. This second alternating current potential is out of phase with the main alternating current source of voltage because of the second phase shifting condenser 51, which causes the control grid-cathode voltage to be out of phase of the anode-cathode voltage of the third and fourth gaseous discharge devices and 2t, The excitation supplied to the motor field l! by the second excitation means |8 will also produce a voltage across the resistors |54 and iti. The voltage developed across the resistor |54 is the potential of the second regulatory means |5|, and, as shown in Figure l, the connection |66 will be negative with respect to the connection 'l0 of the motor eld The potential of the second regulatory means |5| is so connected in the circuit arrangement so as to impress a negative potential upon the control grids of the third and fourth gaseous discharge devices 25 and 26 with respect to the cathodes of these gaseous discharge devices. This negative potential upon the control grids has the tendency to lower the reference voltage of the control grid-cathode voltage with respect to the reference voltage of the anode-cathode voltage. For the condition where there is no voltage from the second output voltage means of the voltage dividing cir- ,z

cuit ll, where the setting of the movable finger |25 of the potentiometer ||9 of the potential source 'l5 is causing the motor to be operated at or below rated speeds, the circuit arrangement is such that a positive potential from the age is to oppose the potential across the end vi,

portion of the voltage dividing resistor ||3 so that the reference voltage of the control gridcathode potential becomes increasingly less positive with respect to the anode-cathode potential, thereby reducing the excitation to the mo f tor field |'l, and consequently increasing the speed of the motor ll. To trace the circuit connections for the control grid-cathode potential, starting with the cathodes 33 and 35, the. circuit extends through the connection 69, the connecthermionic pentode tube 82.

tion 10, through the resistorl54, to the connection |66, wherein a negative potential of the second regulatory means is applied, through the conductors |61 and |65 to the upper terminal of the resistor |40, through the resistor |40 wherein a negative potential of the second output voltage is applied, to the lower terminal |46 of the resistor |40, through the conductor |48 to the terminal |34, through the conductor |35 to the terminal ||6 of the voltage dividing resistor ||3, through a portion of the voltage dividing resistor ||3 to the terminal wherein a positive potential is applied, then through the conductor |68 to the connection 66, and return to the respective control grids 34 and 31 through the third and fourth control grid resistors and 6| wherein the second alternating current potential is applied. As the potential of the second output voltage means increases, by an increasing voltage across the condenser 19 of the potential source 16, an increasingly larger negative potential is applied to the control grid with respect to the cathode of the gaseous discharge devices of the second excitation means. This increasingly negative potential has the tendency to lower the reference voltage of the second alternating current vpotential which is applied across the control grids and cathodes with respect to the main alternating current voltage which is applied across the anodes and cathodes. This tendency will cause the control grids to trigger or fire the gaseous discharge devices later in the cycle thereby tending to reduce the excitation supplied to the second excitation means, and consequently increase the speed of the motor The tendency to reduce the excitation supplied to the motor eld I1 will tend to reduce the potential developed across the resistor |54, which potential is the second regulatory potential, which tendency to reduce the second regulatory potential will tend to raise the reference Voltage between the control grid and cathode with respect to the reference voltage between the anode and cathode, which will tend to increase the excitation means. These two op posing tendencies balance each other in a static condition, however, in a varying condition, the changing potential of the second output voltage lwill prevail, and effect the second excitation means sufiiciently to re-establish the static condition. This second grid circuit means 2| of the control means I9 has the result of obtaining greater than rated speed of the motor |I. The combined operation of the first. and second grid circuit means 20 and 2| of the control means I9 has the resultant effect of permitting conetant acceleration of the motor Il to any predetermined speed up to many times rated speed at a predeterminable variable acceleration rate.

To permit constant deceleration to zero speed of the motor the single pole double throw switch |20 of the potential source 16 can be thrown to exclude the voltage from the unidirectional high voltage source in the circuit arrangement of the potential source 15. When the switch |25 is so thrown, that is when the contact member |24 connects the first connection 2| to the common connection |23, the condenser 19 will be placed across the input terminals of the bridge rectifier 8|, and will discharge through the bridge rectifier and pentode tube 82. The rate of discharge will be constant, as was the rate of charge, because of the constant current passing characteristic of the This rate of discharge will again be regulated by the setting of the movable finger |08 on the potentiometer IUI. Variations in the setting of this movable finger |08 causes variations in the negative potential of the control grid 93 with respect to the cathode 9I of the thermionic pentode tube 82 and therefore vary the amount of current passed by the thermionic pentode tube 82. This has the effect of causing the condenser- 'I8 to discharge at a substantially constant rate, which means the voltage across the condenser I9 Will decrease substantially linearly. This substantially linearly decreasing voltage across the condenser 19, is, as before, applied through the impedance matching circuit 'I8 and the voltage dividing circuit TI, in the form of the first and second output voltages, to modify the control means I 9, to regulate the excitation means and therefore the speed of the motor I I. In a circuit analysis similar to that for an increasing speed of the motor I I by an increasing voltage across the condenser 19, the motor II will be caused to linearly decrease in speed by a decrease in the potential across the condenser 19.

To permit constant deceleration to any predetermined speed of the motor II, with the motor I I running at any given speed, the setting of the movable finger I of the potentiometer IIS may be changed to a lower value. Given this condition, the voltage across the terminals A and B of the condenser 'IS will then be higher than the voltage applied to the circuit of the potential source 'I6 by the setting of the movable finger I25 of the potentiometer IIS. The condenser I9 will therefore discharge through the series circuit arrangement of the high voltage unidirectional source 80 and the bridge rectifier 8|. The rate of discharge will again be governed by the setting of the movable finger IDB of the potentiometer IOI. The rate of deceleration will again be substantially constant, due to the constant current passing characteristic of the thermionic pentode tube 82, and static conditions will again be maintained when the voltage across the terminals A and B of the condenser I9 equals the voltage applied to the potential source 15 by the setting of the movable finger I25 of the potentiometer IIS.

Throughout this description, it has been stated that an essentially linear voltage generated by the potential source 'I6 and applied through the first and second output voltage means of the Voltage dividing circuit 'Il to the control means I9 will cause essentially linear speed control of the motor I I. This characteristic of my invention is accomplished because the potential of t-he regulatory means opposes the potentials of the first and second output voltage means, and since the voltages of the first and second output voltage means are essentially linearly variable, the variations in motor speed will follow an essentially straight line. The effect thereby produced is that in a predetermined set condition, with these two potentials opposing each other, variations in circuit constants due to temperature rise and other variables are cancelled out by the effect of the potential of the regulatory means. In a varying condition, where the speed of the motor I I is being caused to be either linearly increased or decreased, the opposing tendencies of the potentials of the regulatory means and the output voltage means will compensate for hysteresis and armature reaction effect because a tendency to change the output voltage of the generator from that indicated by the setting of the movable finger I25 of the potentiometer IIS will automatically 16 bring a change in the potential delivered from the regulatory means to re-establish the predetermined set conditions as predetermined by the setting of the movable finger I25 of the potentiometer I I9.

From the foregoing description, it may be seen that the linearly variable voltage generated by the potential source I6 may be used to linearly vary the generator output voltage alone, as shown in Figure 2, or the speed of a motor alone, as shown in Figure 3. With reference to Figure 2, it may be seen that the linearly variable voltage of the potential source 'I6 is applied directly to the generator field excitation means I8 to linearly vary the generator output voltage. With reference to Figure 3, the linearly variable voltage of the potential source I6 is applied directly to the motor field excitation means I8 to linearly vary the motor speed.

Although I have described my invention with a certain degree of particularity in its preferred form it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

I claim:

l. An electrical control circuit for varying the speed of an electric motor comprising, in combination, a generator having a field winding and an electrical output, a motor having a eld winding and an electrical input, rst connection means for connecting the electrical output of the said generator to the electrical input of the said motor, rst excitation means including a first gaseous discharge device having a cathode and a control grid for exciting the said generator field Winding, second excitation means including a second gaseous discharge device having a cathode and a control grid for exciting the said motor field winding, control means for varying the speed of the said motor, first grid circuit means impressing a potential between the cathode and the control grid of the said first gaseous discharge device, second grid circuit means impressing a potential between the cathode and control grid of the said second gaseous discharge device, a potential source for modifying the said control means, and a voltage dividing circuit connected between the said potential source and the said control means, the said voltage dividing circuit having first and second output voltage means, the said rst output voltage means modifying the potential impressed between the cathode and control grid of the said first gaseous discharge device for varying the said first excitation means, the said second output voltage means modifying the potential impressed between the cathode and control grid of the said second gaseous discharge device for varying the said second excitation means.

2. An electrical control circuit for varying the speed of an electric motor comprising, in combination, a generator having a field winding and an electrical output, a motor having a field winding and an electrical input, first connection means for connecting the electrical output of the said generator to the electrical input of the said motor, first excitation means including a first gaseous discharge device having a cathode and a control grid for exciting the said generator field Winding, second excitation means including a second gaseous discharge device having a cathode and a control grid for exciting the said motor 12,71 neidfwtnding; @controlfmeansf-for 'varyingthe speed or'tth'e, isaidmotor, 4nrst grid circuit 'means ini` nressingva 'potential between the cathode' and the fcoxitrol,.lgri'd'4 offthesa'id fli's'tfga's'eos discharge dev-ice; second" grid circuit means finpre'ssingi a potential ibetwe'enth'e vcathode andi control grid' of the said second vgase'o'iis l'discharge device, a lpoten'tial scmrce,V for m'odifyviz'i'gv the said control meansf asvoltage dividingl o'eit connected betweenftnefsaidmctennaifsour and' the saldi con-- trolameans, the 'said-voltage dividing circuit' havingfiirst and secondY output' voltage means, the saidnrstfoutput voltagec means rn'od ng the' potential-impressedbetween the catho'deland control. gridofthe-:said nrst gaseous dischargede*- vioefor varying the rsaid first excitation I'ne'ans,L thefsaidse'cond. outputlvoltage ro'difyi g the potentiarimpressea between'the eathodeafrdi control gridfof`V the :Saidiseoondf gaseous discharge deyiceiorfvarying? the I said Secondi felicitation meansmrstlregulatory means having a' regulatory potential .responsive to the electrical outinutof the' saidfigfeiexator fory fiirtlirf modifying the poten; tial impressedfbetween they cathode and control gridaofithe-said'nrst gaseous discharge-device 'for further: varying the", saidrst" excitation' rnans; andsecondfrregulatory means having a regulator-Y potentlal'sresponsive tov the potential applied-1 AtoV the ffsaidl motor" neld fwi'nding for further modifi?- and.4control-grid ofi the said seeondgaseousf dise' charge dcviceffoii inrther-'vaiiying'tl-ie said second excitationmeans.

3; electrical-control circuit 'for 'adynainoelectriclsystemrcomprsing, coinloination;l a gen# erator :havtmlianeld wif iiigj`- and an :electrical Outptitra moto ffhavgfa held-Windingand an electrical inpli't,f*rs`t felicitation Ainea i11l1'1di'rg` a--vst'gaseousidischargedevice' hav'i g1' l'an anode; acathode and acontrol gridfo'r exciting the said generatolfeld winding'glsecond excitation means including as'ecoiidvgaseous discharge device` hav'- ingeaniianod-.fa Adattiene andi a control grid yfor exciting:the-saidimotorlfieldi "winding, afmairi al'- terna'ttng` current' uree oil voltag'ior sp'plv ngi' electricaixenergybetweenthe anode'f andthe cath-- ode.\foifbotli=i..tne nrst. :and second g'aseosy f dis# charge/devices for 'exciting-i tlid-fsald'nrlst and secondfexcitationrmeansscontrol means for varyingfth'efasaid 'excitation vinea-nis; the 'sa`ld-'contro1- meansincluding-z/alrstalteinatingcurrent souiioe ot.lvoltage'elctticallyout of 'iliase' vviththe" A s dimainraiternatingl .currentlsource' o'ivoltagey lfo'rl' inxxiressixrgV at potential; between the?` cathode and` thefcontrol grilli-*of 'the said first?g'asc'a'ousfdis#` chargeadevicef and ai secondlalternating currfe'iit sourceofivoltage electricallyfoutofphasefwitli the'` saidxn'ainalternatingntirrentsource 'of volta'geioi` impressing-i :potentiali betvveen the 'catliodeland controlsgri'd of: -theisaidsecond lgaseo'usdischa device potential.' sourceiforf` modifying "the contro means; s and: 'fa-ff' voltage dividing: `circuit connectedfbetweenathe said' potential?sourcek and f the; said-control f means; ,the said voltage dividing?? cathode and' contrergridofithesaidsecorid'gaseIli 'A ousidischarge 1deviceforva'ryingith'e said secondi excttatiommeanszf 1 4:' l Ameieetrical ycontrollicircuit forf afdynainof Y A said potential sou 18 electra vsystem comprising, in combination', a gemferator having a field winding andv anelectric'al otnut; a motor having a 'eld Winding and ,an

trolv inea'nsvv including'- 'a rst alternating n current source of 'voltag'ele'ctrically outl of phase withr the" `said fniain alternating current source of volti ag'fforfimp'r'ssing a potential between the cathf odfand the control grid ofthe said first gaseous' discharge device and a second alternating cur'- rnt source of voltage electrically out of'phase with thev`4 said ricain alternatingcurrent source of-'vltg for iinijes'sing a potential between th` catloc'ev and the' control grid of the said'first gasois discharge device and a second alterfhating-cdrrent source of voltageelectrically out of nl'ise-'Iwith the Saidjmain alternating current 'son ce' oflvoltagefor impressing a potentialf betweentne cathode' and controlgrd of thesaid secondl gaseousl discharge device, Fa potentialv source for rnodifvingvtiie Vsaid control'mean's; a*

voltage dividingfcircuit connected betvv'een the' l Y, Y'Cafd'the. Said0'ntr01means. thesaidv vol-tag' viding `circuit*havingv `first and` secondoutrint voltagemeans',` the said 'i'irst output'voltage Inaris \mo'difylng the potential irnpressedbetwenf the cathode and control grid of kthe saidanfr'st gaseous discharge device for vary? ing' the: si'd-nrstexeitation means, the' said seeon'd'fotnut voltage' ine'ans modifying vthe' poten?A tial- 'l'lres'sed nl attveen theY cathode `and control grid of :fthf saidsecondgaseous discharge rdevice fo varying fthe said second excitation Inear'isl,I

rstreg'ulatry' yineanls having aregulatorypoten?"v tiarjrsponsite" to vthe electrical output of the said Agenerator for further modifying the potentialimpress/edibetween'the cathode` and Y control' A gaseous discharge devicewforf said rst excitation means;

grifd ofthe said-n firstV furih ,varying the; l l andvsecondiregulatory means having a regulatory charge dev efor'fur'ther varying the said second excitatioimeahs;

hina-tie ,f a generator' having a neldwindingaed an electrical o'iit'piit',l a motor having aeld windmansfoi' connecting the electrical' output of tili-i'sietifgnral)13.1101*` tothe eltr'al input 0f the including a first? 'gaseous'ifdisclar'g' device having? a cathode'l and a'cntrlfgri'dffor exciting the said generato said' niotoi'j firs-t kkexcitation means 'ing'ja second? gaseous 'discharge device havingf'ia excitingthesaid motori field iw'indingj control'- means 7 includingfa:

"d aA `scondgridnircuit means forfvarving thespeed'roff the said` motor; the' said' rst grid' i oirc'itllneansdeveloping a lfirst cathode :and a control grid"V for sprisiv'e tp Vthe potential" appliedy to alternating curl-` rent voltage and impressing the first alternating current voltage between the cathode and the control grid of the said first gaseous discharge device, the said second grid circuit means developing a second alternating current voltage and impressing the second alternating current voltage between the cathode and control grid of the said second gaseous discharge device, a potential source for modifying the said control means, a voltage dividing circuit connected between the said potential source and the said control means, the said voltage dividing circuit having first and second output voltage means, the said first output voltage means modifying the potential impress-ed between the cathode and control grid of the first gaseous discharge device for varying the said i'st excitation means, the said second output voltage means modifying the potential impressed between the cathode and control grid of the said second gaseous discharge device for varying the said second excitation means, first regulatory means having a regulatory potential responsive to the electrical output of the said generator for further modifying the potential impressed between the cathode and control grid of the said first gaseous discharge device for further varying the said first excitation means, and second regulatory means having a regulatory potential responsive to the potential applied to the said motor field winding for further modifying the potential impressed between the cathode and control grid of the said second gaseous discharge device for further varying the said second excitation means.

6. An electrical control circuit for varying the speed of an electric motor comprising, in combination, a generator having a field winding and an electrical output, a motor having a field winding and an electrical input, first connection means for connecting the electrical output of the said generator to the electrical input of the said motor, first excitation means including a first gaseous discharge device having an anode, a cathode and a control grid for exciting the said generator field winding, second excitation means including a second gaseous discharge device having an anode, a cathode and a control grid for exciting the said motor field winding, control means including a first and a second grid circuit means for varying the speed of the said motor, a main alternating current source of voltage for supplying a voltage between the anode and the cathode of both the first and second gaseous discharge devices for exciting the said first and second excitation means, the said first grid circuit means developing a rst alternating current voltage electrically out of phase with the voltage of the said main alternating current source of voltage and impressing the first alternating current voltage between the cathode and the control grid of the said rst gaseous discharge device, the said second grid circuit means developing a second alternating current voltage electrically out of phase with the voltage of the said main alternating current source of voltage and impressing the second alternating current voltage between the cathode and control grid of the said second gaseous discharge device, a potential source for modifying the said control means, a voltage dividing circuit connected between the said potential source and the said control means, the said voltage dividing circuit having first and second output voltage means, the said rst output voltage means modifying the potential impressed between the cathode and control grid of the said first gaseous discharge device for varying the said first excitation means, the said second output voltage means modifying the potential impressed between the cathode and control grid of the said second gaseous discharge device for varying the said secondv excitation means, first regulatory means having a regulatory potential responsive to the electrical output of the said generator for further modifying the potential impressed between the cathode and control grid of the said first gaseous discharge device for further varying the said first excitation means, and second regulatory means having a regulatory potential responsive to the potential applied to the said motor field winding for further modifying the potential impressed between the cathode and control grid of the said second gaseous discharge device for further varying the said second excitation means.

7. An electrical control circuit for varying th speed of an electric motor comprising, in combination, a generator having a field winding and an electrical output, a motor having a field winding and an electric input, first connection means for connecting the electrical output of the said generator to the electrical input of the said motor, first excitation means including a first gaseous discharge device having a cathode and a control grid for exciting the said generator field winding, second excitation means including a second gaseous discharge device having a cathode and a control grid for exciting the said motor field winding, control means for varying the speed of the said motor, the said control means comprising a first and second alternating current voltage means having, respectively, a first and second alternating current voltage, the said first and second alternating current voltage means impressing the said first and second a1- ternating current voltages between the cathodes and the control grids of the said first and second,

gaseous discharge devices, respectively, a potential source for modifying the said control means, a voltage dividing circuit connected between the said potential source and the said control means, the said voltage dividing circuit having first and second output voltage means, the said first output voltage means modifying the potential irnpressed between the cathode and control grid of the said first gaseous discharge device for varying the said first excitation means, the said second output voltage means modifying the potential impressed between the cathode and control grid of the said second gaseous discharge device for varying the said second excitation means, rst regulatory means having a regulatory potential responsive to the electrical out-` put of the said generator for further modifying the potential impressed between the cathode and control grid of the said first gaseous discharge device for further varying the said first excitation means, and second regulatory means havbination, a generator having a field winding and' an electrical output, a motor having a field winding and an electrical input, first connection means for connecting the electrical output of theV said generator to the electrical input of the said motor, rst excitation means including a first gaseous-"discharge device'v having-i an anode, -Ia' cathode and a control'gr'id for exciting the said generator eld winding, second excitation means including a-second gaseous dischargedevice have prising -a` rstand Vsecond alternatin'geurrent voltage means havingfrespectivelyya first-'and secondvoltage electricallyout f- 'pnase with thel voltage of# the lsaid main valternating current means, the said rst and second alternating cur-- rentivoltage meansimpressingfthe said first andY second alternating currentY voltagev between the cathodesand Y the control grids 4ofythe "said rst andi-'second/gaseous discharge devices respece'" tively, a potential source for modifying the said control meansfa voltage dividing circuit cone nectedbetween the said potential source-andthe said control means, the said voltageldividing ci'riv cuit Ihavingfrst and second output/voltage means, the-said'rst output voltage means modi:

fying. :the potential- -impressed between' ythe c'ath-v` ode-and control grid off the said 'first gaseous discharge device-iol'- varying1 the saidflrst e'x'citae'v tionmeansthesaid vsecond output voltage'means modifying the f potential impressedl between the cathodenand-control grid `ofrthe said"second" gaseous'r discharge device -for varyingI the""said second' excitation means,! rst regulatory "means" having .a regulatory-potential responsive to "the electrical output 1 of the'saidfgeneratOrl for fur-"i therv modifying-the potential impressed between the-cathode andcontrol grid ofthe" saidfirst" gaseousA discharge deviceA for further varying the' saidV first excitation means, and secondregulatory means havingaregulatoryv potential responsive' to Vthe potential applied "to the saidl motoriield` winding lforiurther modifying the potential impressed-between the cathode and control grid of the said second gaseous `discharge device for'fiirv ther varying the lsaid second 'excitation means.

9.f In a dynamo-electric system having a generator and a motor, said generator and motor each V1havinga field winding, "first excitation means for exciting the saidI generator eld wind-L ing, second excitation meansvfor exciting the said motor--eld winding, the 'provision of control means comprising a A'potential source having an essentially` linear automatically variable voltage overa first and a second voltage range, rst out# put voltage means for varyingthe said first ex'- citation means -through th'esaid r'st voltage range of the said potential source to vary the output voltage of the said generator, second output'voltage-'means for varying'the said second excitation vmeans throughY the Asaid secondl voltage range of the said potential source 'to vary the.

speed/of the -said motor, circuit means for connecting the said potential "sourceto both the firstand second output voltage means, and velec-- tronic-transition means'for effecting a 'transitionin control'from the said first' output voltage means tothe saidsecondd output' voltage means at' aI denite transitionvalue;

10. AnA electrical control-circuit for essentially linear voltage and f speed control of a dynamoelectric system, comprising, "in combinatio`n,"a`

generator having a fleldwinding and tanz ele'ztri said variable voltage source being ess en t1 al l 70 "and thirdconnection means'for connecting the"v 1- means 'f orexciting"the-said' generator el'dw vdf variable 'voltage source having a 'rstjfand al sec- .variable voltage source, and'` 'nfieans'v for causing" cluding a potential sourcehaving output voltca l output, a motor having a lfield winding an 'electrical input; first' excitation'meanjs :for citing* the *said generator Vfield" winding, 'seco excitation' means "for: e x itir i g`lv the" l said linearly varying the said first and second 'exc tion means to essentiallyV linearly varyk Ithe vspeed of 'the said motoriand-jthe voltage outputY ofthe' saidgenerator, 'the `said 'control "means" including a l' potential i source lfor-l modifying the' saidl 'frstlj andl second excitation'means" and a' lvoltage` viding circuit-connected"between -theis aidpno'te tial source andthe saidvrst c and second'y exc aL tion 'means'. the f' said, vonagedividingv enclin' havingrst and second output voltage 'meansgthej o maare/first actuation, meansrorcbnneamfg die( armature of the' generator *and the :armatiirept the motor in closed circuit:relationshipjand con trol means cfor varying `the *speed ofthe 'zmotoiff' said control means"comprisingiirst 'excitat n" ingr secondrexcitation-*ineans for exciting-the: said motor fieldA winding, anda voltage" dividin circuithavinglfa variable :voltagesource'an A rst anda second output voltage-means; the aid ond "voltag'erange, means for' causingfthe first output-voltage means to: vary the speed 'for 1' the said motor ubelow afpre'determinedf 'speed throughout the' rst voltagerange o f 'the s the said' second output voltage meansto vary"the` speed of the said motor above 4a'predetermined'' speed throughout the secondfvoltage rangeof" said vvariablevoltage source, the' voltagefof/,tli

linearly predeterminably variaple;

122 "In a'dyr'i'amolelec'tric system having agenerator and'airno'tor, said`geneiato1"and motorl each having'a 'field winding, iirst excit ing', a second exoitatin means lfor"'exciting the` Said motor" field Windingf the' rI/)rovison bf con? trol means for controlling thefsaidl rstf afi second excitation means, 'said control 'means/i age means, a' voltage dividingv circuit having" inf put voltage means and'rst'and 'secondfoutput"v voltage' means, 4vfirst connection. 'means' o `r 'co'r'1`f nectingy the said output voltage means lof they `said potential source to thesaid input voltage" means of the said'volta'ge ydividingcircuit,se'cf ond connection means for'conn'ectingth'e said first' output voltage niea'nsorthe said voltage di vidihg circuit to the said first excitation means,`

saids'econd output voltage rneansof the said volte" age dividing'circuit tothe saidsecond excitation I means, the said, potential source supplying an essentially' linearly variable voltage through the Output voltage means thereof to the input voltage means of the said voltage dividing circuit, the said voltage dividing circuit dividing this essentially linearly variable voltage at a definite transition value into a first and a second voltage at the said first and second output voltage means, the said first voltage of the said first output voltage means directly varying the first excitation means and varying directly with the voltage of the potential source until reaching the said definite transition value then remaining constant at this definite transition value for all values of the potential source voltage greater than this value, and the voltage of the said second output voltage inversely varying the second excitation means and remaining at zero until the voltage of the potential source reaches the said denite transition value then varying directly with the potential source above this definite value, and transition means governed by the said control means for effecting a transition from the control of the said first excitation means to the control of the said second excitation means to provide acceleration or deceleration of the said motor to any predetermined speed at an essentially constant acceleration rate, the said acceleration rate being predeterminably variable.

13. In an electrical circuit for essentially linearly varying the speed of an electric motor, the said motor deriving its power from a direct current generator, both the direct current generator and motor having separately excited field windings, first and second excitation means having respectively a first and second gaseous discharge device for exciting the respective generator and motor field windings, the said gaseous discharge devices having a control grid and a cathode, the provision of control means for varying the speed of the said motor by varying the said first and second excitation means, the said control means comprising first and second grid circuit means for applying a potential between the control grids and cathodes of the respective gaseous discharge devices, a potential source for modifying the said control means, a voltage dividing circuit connected between the said potential source and the said control means, the said voltage dividing circuit having rst and second output voltage means, the said first output voltage means modifying the said first grid circuit means, the said second output means modifying the said second grid circuit means, the said potential source having output voltage means with a first and a second output terminal and comprising a bridge rectifier having a first and second input and a first and second output terminals, a unidirectional predeterminably variable substantially constant current passing device connected between the two output terminals of the bridge rectifier, an electrical device, a unidirectional predeterminably variable high voltage source, rst disengageable electrical connection means for connecting the said input terminals of the said bridge rectifier in series circuit relationship with the said unidirectional high voltage source and the said electrical device, and second disengageable electrical connection means for connecting the said input terminals of the said bridge rectifier in series circuit relationship with the said electrical device, the said voltage dividing circuit comprising the output voltage means of the said potential source, a biasing potential source having a first and a second terminal, a thermionic tube having a cathode and an anode, an impedance device having a first and a second terminal, first connection means for connecting the first terminal of the said output voltage means of the said potential source to the first terminal of the said biasing potential source, second connection means for connecting the second terminal of the said biasing potential source to the anode of the said thermionic tube, third connection means for connecting the cathode of the said thermionic tube to the first terminal of the said impedance device, and fourth connection means for connecting the second terminal of the said impedance device to the second terminal of the said output voltage means of the said potential source, the potential of the said first output voltage means appearing across the combination of the biasing potential source and the thermionic tube, and the potential of the said second output voltage means appearing across the said impedance device, means for energizing the said first output voltage means from the said potential source until reaching a predetermined definite transition value then remaining constant at this definite transition value for all values oi the potential source voltage greater than this value, and means for energizing the said second output voltage means from the said potential source at a zero value until the voltage of the potential source reaches the said definite transition value then varying directly with the potential source above this definite transition value, the said first output voltage means directly varying the said first excitation means, the said second output voltage means opposing the said second excitation means, the said control means effecting a transition from the control of the said first excitation means to the control of the said second excitation means to provide essentially linear acceleration or deceleration of the said motor to any predeterminable speed at an essentially constant acceleration rate, the said acceleration rate being predeterminably variable.

14. In a system including a dynamoelectric machine having a field winding and excitation means for exciting said field winding, the provision of control means for varying the excitation means, a potential source having output voltage means, and connection means for connecting said output voltage means to said control means, the said potential source supplying an essentially linearly variable voltage through the output voltage means thereof to said control means, the voltage of said potential source essentially linearly varying the said excitation means to tlius control said dynamoelectric ma.- chine in an essentially linear manner, the said output voltage means of said potential source being first and second output terminals, said potential source including a rectifier having first and second input and first and second output terminals, a substantially constant current passing device connected between the two output terminals of the rectifier, an electrical device, a unidirectional voltage source, first electrical connection means for connecting the said input terminals of the said rectifier in series circuit relationship with the said unidirectional voltage source and the said electrical device, and second electrical connection means for connecting the said input terminals of the said rectifier in series circuit relationship with the said electrical device, the said first and second output terminals of said potential source being connected across said electrical device.

15. In a system including a dynamoelectric machine having a field winding and excitation means for exciting said eld winding, the provision of control means forvarying the excitation means, a potential source having output voltage means, and connectionV means for connecting said output-voltage means to said control means, the potentialr source supplying an essentially linearly variable voltage through the output voltage means thereofto said control means, the voltage of said potential source essentially linearly varying thel said excitation means to thuscontrol said dynamoelectric machine in an essentially linear manner, the said output voltage means of said potential source being first and second output terminals, said potential source including a bridge rectiiier having first and second input and first and second output terminals, a unidirectional predeterminably variable substantially constant current passing device connected between the two output terminals of the bridge rectifier, an electrical energy storage device, a unidirectional predeterminably variable voltage source, iirst disengageable electrical connection means for connecting the said input terminals of the said bridge rectier in series circuit relationship with the said unidirectional voltage source and the said electrical energy storage device, and second disengageable electrical connection means for connecting the said input terminals of the said bridge rectier in series circuit relationship with the said electrical device, the said iirst and second output terminals of said potential source being connected across said electrical, energy storage device.

16. In a motor control system having a motor with a iield winding and excitation means for exciting said field Winding, the provision of control means for varying the excitation means, a potential source having output voltage means, and connection means for connecting said output voltage means to said control means, the said potential source supplying an essentially linearly variable voltage variable at a predeterminably variable rate through the output voltage means thereof to said control means, the voltage of said potential source varying the said excitation means to thus control the speed of said motor at predeterminably variable rates, the said output voltage means of said potential source being first and second output terminals, said potential source including a rectiiier having iirst and second input and iirst and second output terminals, a substantially constant current passing device connected between the two output terminals of the rectiiier, an electrical device, a unidirectional voltage source, first electrical connection means for connecting the said input terminals of the said rectiiier in series circuit relationship with the said unidirectional voltage source and the said electrical device, and

second electrical connection means for connecting the said input terminals of the said rectifier in series circuit relationship with the said electrical device, the said first and second output terminals of said potential source being connected across said electrical device.

17. In a generator control system having a generator with a eld winding and excitation means for exciting said eld winding, the provision of control means for varying the excitation means, a potential source having output voltage means, and connection means for connecting said output voltage means to said control means,

, Y .26 l the 'said-potential source supplying an essentiallylinearly variable voltage through the output voltage means thereof to said control means, the voltageof saidpotential source essentially linearly varying the said excitation means to thus control'thevoltage of said generator in an essentially linear manner, the said output voltagemeans of said potential source being rst and" second output terminals, said potential source includinga rectiiier having rst and second input and'nrst and second output t'erminals, a substantially constant current passing device `connected between the two output terminals of'the rectiiier, an electrical device, a unidirectional voltage source, rst electrical connection means for connecting the said input terminals of the said rectifier in series circuit relationship with the said unidirectional voltage source and the said electrical device, and second electrical connection means for connecting the said input terminals of the said rectier in series circuit relationship with the said electrical device, the said rst and second output terminals of said potential source being connected across said electrical device.

18. In a dynamoelectric system having a generator and a motor, said generator and motor each having a field winding, first excitation means for exciting the said generator iield winding, and second excitation means for exciting the said motor eld winding, the provision of control means comprising, an automatically variable voltage for controlling said excitation means, said voltage adapted to exceed a definite voltage value, and transition means for effecting a transition in control from the first to the second excitation means as said variable voltage exceeds said definite voltage value.

19. In a system including a dynamoelectric machine having a field Winding and excitation means for exciting said eld winding, the provision of control means for varying the excitation means, a potential source having output voltage means, and connection means for connecting said output voltage means to said control means, the said potential source supplying a voltage variable at a predeterminably variable rate through the output voltage means to said control means, the voltage of said potential source varying the said excitation means to thus control a characteristic of said dynamoelectric machine at predeterminably variable rates of change of said characteristic, said potential source including an electrical energy storage device with the output voltage means connected thereacross, a unidirectional voltage source, and connection means for connecting said unidirectional voltage source to said electrical device to store electrical energy therewithin.

20. In a system including a dynamoelectric machine having a iield winding and excitation means for exciting said field winding, the provision of control means for varying the excitation means, a potential source having output voltage means, and connection means for connecting said output voltage means to said control means, the said potential source supplying a voltage variable at a predeterminably variable rate through the output voltage means to said control means, the voltage of said potential source varying the said excitation means to thus control a characteristic of said dynamoelectric machine at predeterminably variable rates of change of said characteristic, the said output voltage means of said potential source being rst and second output terminals, said potential source including a rectifier having first and second input and rst and second output terminals, a substantially) constant current passing device connected between the two output terminals of the rectifier, an electrical device, a unidirectional voltage source, rst electrical connection means for connecting the said input terminals of the said rectier in series circuit relationship with the said unidirectional Voltage source and the said electrical device, and second electrical connection means for connecting the said input terminals of the said rectifier in series circuit relationship with the said electrical device, the said rst and second out- 28 put terminals of said potential source being connected across said electrical device.

JAY W. PICKING.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 773,836 White Nov. 1, 1904 865,822 Bogen Sept. 10, 1907 2,229,968 Garman Jan. 28, 1941 2,255,488 Huston Sept. 9, 1941 2,301,689 Edwards et al` Nov. l0, 1942 2,393,618 Edwards et al Jan. 29, 1946 

